Many scientific and engineering applications require the ability to detect and analyze the time profile of fast-occurring events. For instance, many research projects involve the study of light emission (e.g., laser pulses, photoluminescence, electro-luminescence, etc.) which has very short duration, typically ranging from nanoseconds to sub-picoseconds, and it is necessary to know how the intensity and spatial distribution of the light changes as a function of time. Due to the very short durations of such events, however, it can be quite a challenge to record the time information of the event progression, and some creative ways have to be implemented to convert the time information into some other quantities that can be more easily measured.
For example, a streak camera is often used to analyze the time profile of laser pulses. The streak camera converts an incident laser pulse into photoelectrons, which are deflected to different angles based on their arrival time and projected onto a phosphorus screen to form a streak of light, and the position in the streak corresponds to the time of incidence of the photons in the pulse. The streak image is captured using a charge coupled device (CCD) so that it can be stored and analyzed to derive the time profile of the laser pulse. In this example, the steak camera functions as a time-to-space converter. There are also other approaches to measuring the time profiles of fast events, such as converting time into the amplitude of an electrical pulse. Those conventional time measurement approaches have various issues and disadvantages. For instance, time-to-space converters tend to be very large, and time-to-amplitude converters produce electric pulses that by nature are volatile and have to be detected by other means.